Terms like “upper” and “lower” refer to the positions of the various components in the position of application.
When petroleum wells are being established from the seabed, it is common first to insert a conductor casing into the seabed. The seabed often consists of relatively loose sediments. Drilling of the petroleum well itself is carried out via the conductor casing. A valve arrangement located above the seabed is connected to the well in such a way that loads from the valve arrangement, which may be of a considerable weight and dimension, are transmitted to the conductor casing. A good and secure mounting to the seabed is essential, especially for the conductor casing to be able to resist the prevailing fatiguing forces.
Experience has shown that conventional methods of attachment between the conductor casing and the seabed give an unreliable and often insufficient attachment. The applicant's Norwegian patent application 20140210 discloses a mounting of a conductor casing by means of a suction foundation, which is provided with a supporting pipe. The suction foundation with the supporting pipe is inserted into the seabed in a manner known per se. The conductor casing is moved further into the seabed via the supporting pipe. Filling cement slurry into the annulus that forms between the supporting pipe and the conductor casing is one way of providing a substantially improved and secure mounting of the conductor casing. Other ways of fixing it are also known.
By relatively shallow reservoirs, for example, it may be practical to divert the well pipes from the vertical direction as high up as possible below the seabed. This may be achieved by slanting at least a portion of the conductor casing.
The device according to NO 20140210 has not been adapted for conductor casing to be slanted.
WO0165050 A1 discloses a suction substructure arranged for use in the installation of at least one conductor casing string in at least one well on or in a seabed, wherein a conductor casing shoe is provided in the lower end of the conductor casing string. One embodiment comprises an inclined conductor casing string.
U.S. Pat. No. 4,258,800 discloses a conductor casing shoe provided in the lower end of a conductor casing string for deflecting a conductor in a desired direction, wherein the casing shoe opening is eccentric relative to an upper support pipe, wherein the center axis of the casing shoe is slanted relative to the center axis of the supporting pipe.